Static electricity preventing method and member using the method

ABSTRACT

The present invention provides a new antistatic method and its application to members. The present invention is an antistatic method featured to mount multiple resin based composites with different triboelectric series order on the surface and members featured to have multiple resin based composites with different triboelectric series order on the surface. The members are resin based sheets, resin based films or resin molded materials. The resin based composites are adhesives, bonding agents, printing ink or paint.

TECHNICAL FIELD

The present invention relates to an antistatic method and itsapplication to members.

BACKGROUND ART

It is demanded to reduce the generation of static electricity in variousfields and applications such as packaging containers for electroniccomponents and surface protection films stuck on polarizing plates forliquid-crystal display panels. The packaging container for electroniccomponents is, for example, an embossed carrier type taping with whichthe electronic components are housed in the embossed part of the carriertape and sealed by thermal fusion so as to cover the embossed part bythe cover tape. The packaging containers include also magazines, traysand bags. Static electricity is generated by the contact of electroniccomponents and packaging containers. Static electricity has a risk ofdeterioration and destruction for electronic components. Contacting thepackaging containers at each other or contacting the packaging containerwith other materials generate static electricity and might lead todeterioration or destruction of the electronic components through thepackaging container. Conductivity or antistatic property has been addedto the packaging containers for the prevention. This prevention methodis effective for discharge or attenuation of the generated staticelectricity in an early stage. However, it is difficult to reduce thegeneration of static electricity itself.

A surface protection film has been stuck on a liquid-crystal displaypanel in the manufacturing process. Static electricity is generated inexfoliating the surface protection film from the surface ofliquid-crystal display panel. Some problems caused by static electricityinclude induction of the poor appearance occurred by sticking dust tothe panel surface, occurrence of abnormal displaying, malfunction of thedisplay unit or induction of electrostatic destruction of the driveelements.

JP-8-245932, JP-9-267449 and JP-11-256115 have been proposed as a methodusing the antistatic treated resin films treated on at least one side ofthe resin films by antistatic agents such as alkali metal ion,quaternary ammonium salts and metal oxides as member layers constitutingthe adhesive tape. JP-6-83267 has been disclosed as a method that kneadsconductive agents into adhesive layer itself. These both methods do notsuppress the generating static electricity, but prevent electrostaticfault by early discharge and attenuation of the generated staticelectricity.

DISCLOSURE OF THE INVENTION

The inventors have noticed that it is important to suppress thegeneration of static electricity itself in order to preventelectrostatic failures and obtained the following knowledge. Thegeneration of static electricity may be prevented by mounting multipleresin based composites with different triboelectric series order on thesurface. The member mounted multiple resin based composites withmultiple different triboelectric series order on the surface maysuppress the generation of static electricity even when electroniccomponents and the like are handled on the mounted surface and mayprevent the electrostatic failures of electronic components.

Thus, the present invention presents the following points:

-   1. an antistatic method featured to mount multiple resin based    composites with different triboelectric series order on the surface,-   2. the antistatic method according to 1, wherein multiple resin    based composites with different triboelectric series order comprise    resins electrified more positively and more negatively than the    electrification-controlled object,-   3. the antistatic method according to 1 or 2, wherein multiple resin    based composites differ more than 0.1 nC in the amounts of    electrified charge,-   4. the antistatic method according to 1, 2, or 3, wherein multiple    resin based composites are adhesives, bonding agents, printing ink    or paints,-   5. the antistatic method according to 1 to 4, wherein members are    resin based sheets, resin based films or resin molded materials,-   6. members featured to have layers of multiple resin based    composites with different triboelectric series order on the surface,-   7. the members according to 6, wherein the thickness of the layer of    resin based composites is 0.1 to 10,000 μm,-   8. the members according to 6 or 7, wherein members are resin based    sheets, resin based films or resin molded materials.

BRIEF DESCRIPTION OF DRAWING

FIG. 1 is a schematic view of an instrument for measuring the amount ofpeeling electrification. Meanings of each code are as follows: 1,deposited subject, 2, measuring instrument, 3, observation window, 4,metal plate, 5, conducting wire, 6, coulomb meter, 7, measuring probe,8, conducting wire, 9, conducting wire, 10, switch, 11, antistaticplate, 12, samples, 13, clamp, 14, insulator, and 15, metallic measuringdesk.

FIG. 2 is a schematic view of an object 1 on which is mounted a sample(adhesive tape) 12 containing first resin based layers 20 and secondresin based layers 30 arranged side-by-side along a surface of theobject 1.

BEST MODE FOR CARRYING OUT THE INVENTION

A triboelectric series is a list that enumerate materials in thepositive and negative polarity order by the charge generated in rubbingtogether two materials and is one of the methods for understanding theelectrical properties of various materials. The following triboelectricseries is known for main resins used as principal ingredient inadhesives and printing ink:

-   positive side,-   silicone resin,-   acrylic resin,-   urethane resin,-   vinyl based resin,-   negative side.-   The following triboelectric series is known for main resin:-   positive side,-   polymethyl methacrylate resin,-   polystyrene resin,-   polyester resin,-   polyethylene resin,-   polypropylene resin,-   polyvinyl chloride resin,-   polytetrafluoroethylene resin,-   negative side.    The triboelectric series order is not limited to the aforesaid. The    triboelectric series order may be easily measure by positive or    negative charging in rubbing together two materials.

In the present Invention, resin based composites are ones which containresins as its main components, such as adhesives, printing ink, coatingmaterials. As the adhesives, various known types of adhesives such assolvent type, emulsion type, hot melt type and reaction type may beused. For the printing ink, commercially available ink used vinyl basedresin, polyurethane based resin, polyacryl based resin, polyester basedresin, etc. as binder resins may be used.

In the present invention, multiple resin based composites with differenttriboelectric series order means composites comprised two or moredifferent resins, preferably two or three ones, and also include asingle composite comprising multiple resins with different triboelectricseries order. These resin based composites may be mounted on the surfaceof members in a stratified pattern, for example, by coating adhesives onthe surface of members comprising sheets or films by means of a screenmethod, a photogravure method or a mesh method for the adhesives. Forthe printing ink, the coated films may be obtained on sheets, films andmolded products by means of a spraying method, a bar code method, adoctor blade method, a roll coating method, a screen method, aphotogravure method, a mesh method, etc. through coating, drying andremoval of organic solvent. In the case of the adhesives and theprinting ink, the thickness of the layers of resin based composites isnot restricted particularly and may be adjusted corresponding to thepurposes, however, generally the thickness of 0.1 to 10,000 μm, morepreferably 5 to 5,000 μm is selected.

The method for mounting multiple resin based composite with differenttriboelectric series order on members may form the resin basedcomposites in arbitrary patterns such as stripe, dot and mesh. Withoutlimiting to these patterns, however, the resin based composites may becoated in random shape. For example, multiple resin based compositeswith different triboelectric series order may be produced also bycoating the resin based composites with different triboelectric serieson the coated surface in stripe, dot and mesh patters after coatingresin based composites wholly on the surface of members. Resin basedcomposites with the difference of 0.1 nC or more, especially thedifference of 0.5 nC or more in electrified charge are preferable tousing as the resin based composites with different triboelectric seriesorder. For example, resin based composites for measuring are placed on aslope with an angle of 20 degree. By rolling a cylinder made of Teflonand/or quartz on the slope, amounts of electrified charge on thecylinder are measured using the charge measuring instrument;Triboelectric Charge Generation Test System Model 705 of Electro-TechSystem Inc. When it is difficult to apply this charge measuring methodbecause of stickiness of the resin based composites or some otherreason, the measurement may be carried out by the determination of anamount of electrification (call ‘amount of peeling electrification’ inthe followings) in peeling of the said adhesive tape from the objectwith the instrument of FIG. 1. When objects to be prevented againstelectrification are apparent, combined use of resins electrifying morepositively and resins electrifying more negatively than the charge ofthe objects is preferred for the resin based composites with differenttriboelectric series order in the invention.

Static electricity is generated between adhesion layer of adhesive tapeand the pasted object when the adhesive tape is pasted on the object andpeeled. The generation of static electricity is suppressed by usingadhesives with different resin composition for the adhesion layerbecause of different triboelectric series. For example, in using acrylicresin for the pasted object and using silicone resin and vinyl resin forthe adhesion layer, positive static electricity is generated since thesilicone resin is positive against the acrylic resin in triboelectricseries, while negative static electricity is generated in case of vinylbased resin. Thus, the generation of static electricity is suppressed bycanceling each other. Even when the resin compositions of principalingredients of two different adhesives are the same, resins may be usedalso which are altered the triboelectric series order by the differenceof compounding ratio of crosslinking agents, additives and auxiliary canbe used also.

The members are, for example, sheets, films and molded materials,preferably with the thickness of 0.1 to 10,000 μm. Multiple resin basedcomposites with different triboelectric series order may be produced onthe surfaces of these members. The members may have the structure withadhesives or printing ink coatings. Multiple resin based composites withdifferent triboelectric series order may be mounted on the surface ofmembers by the coextrusion of two or more resin based composites. Themolded materials may be also obtained by thermal molding of sheets withantistatic performance.

In the present invention, multiple resin based composites withtriboelectric series order is desirable to mount on the surface of resinbased members to generate easily static electricity. Resins for themembers have no restriction, but it is suitable to use resins with whichthe triboelectric series differ from that of resin based compositesmounted on the surface of members. For example, the following may beused for the members: polystyrene, polyolefins, polyesters,polycarbonates, acrylic resin, polyamides, polyurethane, polyvinylchloride, epoxy resin, phenolic resin, their modified materials andtheir blend or alloyed products. For these resins, commerciallyavailable resins may be used without modification. These resins may beused alone or as a blend of two or more resins and mixing of otheradditives is also allowed.

Multiple resin based composites with different triboelectric seriesorder are mounted on the surface of sheets or films by means of themeasures such as coating and printing. By adhering and transferring themounted sheets or films to the surface of molded products, multipleresin based composites with different triboelectric series order may beproduced on the surface of molded products. The molded products include,for example, the followings: carrier tapes for semiconductortransportation, trays for semiconductor transportation, containers forLCD module transportation, containers for PDP module transportation,containers for circuit board transportation, containers for mountedboard transportation, containers for hard disk transportation, trays forhard disk head transportation and the like. Parts used for paper feedingand parts contacted with paper in printers and copying machines areeasily charging parts and the method for suppressing the staticelectricity in the present invention may be used for these parts. Themethod may be used in order to prevent the adsorption of dust caused bycharging. The objects include cabinets for television, CRTs, personalcomputers, printers, copying machines and the like. Blackened dirtoccurred by electrostatic attachment of dust can be prevent by themethod. The method may be used in order to prevent the adsorption ofdust caused by charging. For example, if the method is applied to themembers used for wall surface and ceiling in clean rooms, the stickingof dust and the lowering of cleanness caused by whirling up the adsorbeddust in the air by certain cause can be prevented. For example, if themethod is applied to the members used for wall surface and ceiling inhospitals, the members used for wall surface and ceiling in foodprocessing factories and the members used for dustprotector forproduction line in food factories, the adhesion of dust may be similarlyprevented.

In these examples, multiple resin based composites with differenttriboelectric series order are mounted on the surface of sheets or filmsby means of the measures such as coating and printing, and multipleresin based composites with different triboelectric series order areproduced on the surface of molded products by adhering and transferringthe mounted sheets or films to the surface of molded products. Withoutusing this method, multiple resin based composites with differenttriboelectric series order may be also mounted directly on the surfaceof molded materials by means of the measures such as painting andprinting.

For the sheets and the films, multiple adhesives comprising multipleresin based composites with different triboelectric series order maycoated on the surface in the present invention. An example applied thismethod is the suppression of peeling electrification generated inexfoliating these adhesive sheets and adhesive films. For example, theyinclude dicing tapes, background tapes and various protective films usedin order to protect the optical parts in LCD modules. They prevent thepart destruction caused by peeling electrification generated inexfoliating the adhesive sheets and the adhesive films. Otherapplication examples of the adhesive sheets and the adhesive films areprotective sheets and protective films used to prevent the scratch ordirt of metal plates, decorative plywoods, plastic plates and variousproducts and are curing sheets and curing tapes used to prevent theparts not to be painted in painting external walls of houses or metalproducts. It may be prevented that these adhesive sheets and adhesivefilms cling to the hand of the worker or the surrounding members bypeeling electrification generated in peeling after their use.

In the present invention, moreover, multiple resin based composites withdifferent triboelectric series order are mounted on the surface ofsheets or films by means of the measures such as coating and printingand the mounted sheets or films are adhered or transferred to thesurface of molded products. As another case, multiple resin basedcomposites with different triboelectric series order are mounteddirectly on the surface molded materials by means of the measures suchas painting and printing and arbitrary electrification is generated bythe mounted resin based composites. An application example of thismethod is electrostatic adsorption. For example, in its application toair filter, dust in the gas passing in the filter is charged andadsorbed. For example, in its application to notice boards, paper sheetsor films to be noticed on the board are stuck by rubbing and charging.

EXAMPLE 1

A sticky solution which was a mixture of 100 weight parts of additionreaction cross-linking type silicone adhesive (manufactured by DowCorning Toray Silicone Co. Ltd., SD 4580, the amount of electrifiedcharge of +1.5 nC) and 0.9 weight parts of a curing agent (manufacturedby Dow Corning Toray Silicone Co. Ltd., NC 25) was coated on one side ofpolyester film (manufactured by Teijin DuPont Film Ltd. PET-SL) withthickness of 38 μm by a bar coater so as to form a strip with width of 5mm. The thickness after two minutes drying at 100° C. was about 10 μm.Next, a sticky solution which was a mixture of 100 weight parts ofacrylic adhesive (manufactured by Soken Chemical and Engineering Co.,Ltd., SK Dyne 1473H) and 3.0 weight parts of a curing agent (NipponPolyurethane Industry Co., Ltd., Coronate L-45) was coated by a barcoater so as to form a strip with width of 5 mm without superposing onthe formerly applied adhesive. The thickness after 1 minute drying at100° C. was about 10 μm.

EXAMPLE 2

For impact resistant polystyrene resin, a sheet-like resin was obtainedby extruding the molten resin from a single-layer T-shape die of 1300 mmwidth using a single screw extruder (non-vent) with screw of 90 mmdiameter and by cooling using the three-cooling-roller method. Two typesof printing ink with different resin composition, comprising apolyvinylidene fluoride/acrylic (7/3) copolymer resin (0.0 nC of theamount of electrified charge against Teflon cylinder) and an acrylicresin (−1.8 nC of the amount of electrified charge against Tefloncylinder) ingredients, were coated on the surface of the said sheetusing a photogravure coater so as to form stripes of regular intervals.

EXAMPLE 3

The coated sheet obtained in the example 2 was slit to 8 mm width,followed by punching guide holes and by compression molding to afford acarrier tape.

COMPARATIVE EXAMPLE 1

A sticky solution which was a mixture of 100 weight part of acrylicadhesive (manufactured by Soken Chemical and Engineering Co. Ltd., SKDine 1473H) and 1.0 weight part of a curing agent (manufactured byNippon Polyurethane Industry Co., Coronate L-45) was coated wholly onone side of polyester film (manufactured by Teijin DuPont Film Ltd.PET-SL) with thickness of 38 μm by a bar coater. The coated film wasdried for two minutes at 100° C. The thickness of the adhesive layer wasabout 10 μm.

COMPARATIVE EXAMPLE 2

After 10 weight part of carbon black and 90 weight part of impactresistant polystyrene resin was measured respectively and mixeduniformly using a high speed mixer, the mixture was kneaded using aventing twin screw extruder with screw of 45 mm diameter and waspelletized by a strand cut method to afford a conductive resin basedcomposite. A sheet of 300 μm thickness was obtained from the conductiveresin based composite by using an extruder (L/D=26) with screw of 40 mmdiameter.

Evaluation of the Antistatic Performance

For the adhesive tapes, the sheets and the molded materials obtainedthese examples and comparative examples, the antistatic performance wasevaluated according to the followings.

EXAMPLE 1 AND COMPARATIVE EXAMPLE 1

To evaluate the antistatic performance of the adhesive tapes obtained inExample 1 and Comparative example 1, the amount of electrostatic charge(call “amount of peeling electrification” in the following) inexfoliating the adhesive tape from its objects was measured using theinstrument shown in FIG. 1. The objects were a TAC (triacetyl cellulose)film, PET (polyethylene terephthalate) film and PE (polyethylene) filmof 50 μm thickness.

In FIG. 1, the object 1 was placed on the metal plate 4 and fixed by theclamp 13 so that the object 1 could not move. The metal plate 4 wasdesired to have a larger area than that of the object in order to catchall electric lines of force generated by the peeling electrification inthe side of object 1 contacted with the metal plate 4 to enhance themeasurement accuracy. The metal plate 4 was connected by the conductingwire 5 to the measurement probe 7 in the coulomb meter 6 which was adevice for measuring electric charge. The coulomb meter 6 was alwaysconnected to the earth by the conducting wire 8. The coulomb meter was ameasuring instrument based on the principle that stored once electriccharge in a capacitor and measured the stored electric charge.Commercially available coulomb meter could be used without modification.

The metal plate 4 was connected to the earth by the conducting wire 9through the switch 10. In addition, the metallic antistatic plate 11with an area similar to or larger than the area of the object 1 wasprepared separately. Any metallic plates could be used as the antistaticplate 11. The antistatic plate 11 was desirable to have an area to fullycontact with the largest one among the object and adhesive tape.

The metal plate 4 was fixed on the metallic measuring desk 15 throughthe insulator 14. Any materials that gave electrical insulation and weredifficult to be charged, for example, ceramics and glass (particularlyceramics are preferable), might be used as the insulators 14.

The charge was generated on the object 1 by the peeling in exfoliating asample 12 such as adhesive tape pasted on the object 1. Charges withopposite polarity was generated on the metal plate 4 contacted with theobject 1 in exfoliating a sample 12 and charges with the same polarityas charges generated simultaneously on the object 1 was transferred tothe measurement probe 7 in the coulomb meter 6 through the conductingwire 5 and was displayed as the then charge amount of peelingelectrification on the coulomb meter 6.

The amount of peeling electrification generated on the whole object 1might be measured because all charges generated on the whole object 1was acquired by using the metal plate 4.

The profile of the amount of peeling electrification might be determinedby plotting the charge for time axis since the charge was generatedaccording to the peeling of the adhesive tape 12. The measuring devicewas desirable to be shielded by electroconductive materials connectedwith the earth (it is not illustrated in FIG. 1). Electroconductivematerials were materials with electroconductivity. For example, metallicmaterials or metallic materials holed in the degree that does not affectthe measurement might be used as electroconductive materials, but theelectroconductive materials were not limited to these. Among themeasuring instruments, the resin-containing products such as the coulombmeter 6, the measuring probe 7 and the switch 10 were desirable to beplaced on the outside of the shields.

The amount of peeling electrification in exfoliating completely theadhesive tape was measured using the aforesaid instruments in thefollowing conditions and the results were described in Table 1.

The object 1 was fixed by the clamp 13 to the metal plate 4 which hadthe same area (125 mm×50 mm) as the object 1 and was placed on theinsulator (ceramics), and the adhesive tape of 125 mm×25 mm (theactually pasted part of 100 mm×25 mm) was pasted on the object 1 in aspeed of 300 mm/min by a roller conformed to JISZ-0237. Moreover, theantistatic plate 11 was placed on the adhesive tape and the metal plate4 was switched to the earth by the switch 10 simultaneously and left for30 second. Then, the antistatic plate 11 was removed quickly and themetal plate 4 was disconnected from the earth by switching of the switch10. The amount of peeling electrification was measured by exfoliatingthe adhesive tape at a speed of 500 mm/second using ceramic tweezers.The object pasted with the adhesive tape beforehand could be used also.The metal plate 14 was made of stainless steel described in JISG4305 andits thickness was 1.5 mm. Its surface was marked lightly by No. 280waterproof abrasive paper described in JISR6253 in the axial directionof the test plate and was ground uniformly in length direction over thefull length until the mark disappeared completely. The antistatic plate11 was made of stainless steel described in JISG4305 and its thicknesswas 1.5 mm. Its surface was marked lightly by No. 280 waterproofabrasive paper described in JISR6253 in the axial direction of the testplate and was ground uniformly in length direction over the full lengthuntil the mark disappeared completely. NK-1001 of the Kasuga ElectricWorks Co., Ltd was used as a coulomb meter.

TABLE 1 TAC film PET film PE film Example 1 −15.0 nC −18.0 nC  −3.0 nCComparative −31.7 nC −22.0 nC −17.7 nC example 1

As shown in Table 1, the measured amount of peeling electrification forthe samples coated alternately two different adhesives in Example 1showed smaller values than those of singly coated samples in Comparativeexample 1. This tendency is recognized on any objects. Thus, it wasfound that the amount of peeling electrification could be controlled andthe antistatic performance was excellent.

EXAMPLE 2˜3 AND COMPARATIVE EXAMPLE 2

An IC was placed on the sheets or the molded products according to theExample 2˜3 and Comparative example 2 and was rubbed with a vibrator ata vibration speed of 600 times/minute for 30 seconds, and then, the ICpicked up by ceramic tweezers was thrown into a Faraday cage and thecharge generated on the rubbed surface of the IC is measured. For themeasurement of the amount of electrificated charge, Nano coulomb meterand Faraday cage of Electro-Tech System Co. were used.

TABLE 2 amount of electrificated charge Example 2   0.20 nC Example 3  0.14 nC Comparative example 2 −2.56 nC

As shown in Table 2, the charge generated on the surface was reduced bymounting multiple resin based composites with different triboelectricseries order on the surface and the members with excellent antistaticperformance could be obtained.

INDUSTRIAL APPLICABILITY

By producing intentionally the structure of which two or more resinbased compositions with different triboelectric series order are exposedto the most exterior surface of members at least on the one side,antistatic materials which control the static electricity generated bypeeling, contact or friction may be obtained. The use of the obtainedantistatic materials enables to reduce all electrostatic failures forany adhered materials, contents, or resin types and forms of frictionmaterials.

1. An antistatic method comprising mounting a layer consisting of curedsilicone resin and a layer consisting of cured acrylic resinside-by-side along a surface of a member; and peeling the layerconsisting of cured silicone resin and the layer consisting of curedacrylic resin from the surface of the member.
 2. The antistatic methodaccording to claim 1, wherein the layer consisting of cured siliconeresin and the layer consisting of cured acrylic resin are, respectively,electrified more positively and more negatively than the member.
 3. Theantistatic method according to claim 1, wherein the layer consisting ofcured silicone resin and the layer consisting of cured acrylic resindiffer more than 0.1 nC in the amounts of electrified charge.
 4. Theantistatic method according to claim 1, wherein the member is a resinbased sheet, resin based film or resin molded material.
 5. Theantistatic method according to claim 1, wherein each of the layerconsisting of cured silicone resin and the layer consisting of curedacrylic resin is mounted on the surface of the member in a patternselected from the group consisting of a stripe, a dot and a mesh.